It is known that alkynes can be converted to acyclic and cyclic oligomers with the aid of catalysts containing transition metals. As a rule, the catalysts used for producing substituted benzene derivatives by cyclotrimerization of alkynes contain complex compounds of nickel or cobalt.
Cobalt compounds seem to favor the formation of 1,2,4-substituted aromatics from 3-hydroxy-1-alkynes (see Chini et al., J. Chem. Soc. C, 1967, 830; and Chukhadzhyan et al., Zh. Org. Khim., 8, 1972, 119; Id.. 10, 1974, 1408). When propargyl alcohol is polymerized in the presence of Ni(CO).sub.2 (P(C.sub.6 H.sub.5).sub.3).sub.2, a mixture of 1,3,5- and 1,2,4-tris(hydroxymethyl)-benzene is obtained as well as some difficult-to-remove byproducts in a vigorous reaction (see Reppe et al., Liebigs Ann., 560, 1948, 104).
In Ger. Pat. 1,159,951, carbonyl-free phosphite- and thiophosphite-containing nickel catalysts are described which are suitable for the cyclooligomerization of 3-hydroxy-1-alkynes, e.g., 3-methyl-1-butyne-3-ol. Good yields can be obtained with these catalysts under relatively mild conditions. Particularly good results have been obtained when the aryl phosphite ligands of the catalyst contain voluminous substituents on the aromatic nucleus in the position ortho to the oxygen. A disadvantage of such catalysts is that the nickel-containing precursors subsequently reacted with suitable phosphites to obtain the target catalysts are, e.g., bis(acrylonitrile)-nickel(O), bis(acrolein)-nickel(O), or bis(duroquinone)-nickel(O), and are obtained from highly toxic nickel tetracarbonyl. The same reservation applies to the catalysts described in Ger. Pats. 2,046,200 and 2,056,555, which are produced from Ni(CO).sub.4 and triaryl phosphites, and which are also suitable for, e.g., cyclooligomerization of 3-methyl-1-butyne-3-ol. Since it is desirable to minimize or avoid the use of toxic compounds like Ni(CO).sub.4 in industrial processes in order to make production methods safe and environmentally benign, catalysts made from nickel tetracarbonyl like those described above are disfavored due to their danger.
There are references in the literature to carbonyl-free catalysts for cyclooligomerization of 3-hydroxyalkynes, particularly of 3-methyl-1-butyne-3-ol, but the systems described heretofore still are beset with disadvantages which militate against their use in industrial production. An example is bis(tributylphosphine) nickel(II) halides (see Gazz. Chim. Ital., 103, 1973, 849), of which the most noteworthy representative is (Bu.sub.3 P).sub.2 NiBr.sub.2 on account of its activity and selectivity in the trimerization of 3-methyl-1-butyne-3-ol. This catalyst displays its catalytic activity only after an incubation time of indeterminate duration in the presence of 3-methyl-1-butyne-3-ol, wherewith after completion of the catalyst formation the 3-methyl-1-butyne-3-ol cyclooligomerizes exothermically, with a rapid rise in temperature which can be controlled only with difficulty. This drawback is in addition to the high cost of the nickel bromide-phosphine complex and the fact that the complex contains a halide which is undesirable. Also, the 1,3,5-tris(.alpha.-hydroxyisopropyl)-benzene raw product obtained with this catalyst (in hexane at 60.degree. C.) contains nickel in an amount of 1,500-2,000 ppm, which represents a high content of heavy metal. Accordingly, in a number of areas of application, this product must undergo subsequent purification which is costly and entails product losses.
Another carbonyl-free nickel catalyst for cyclotrimerization of 3-methyl-1-butyne-3-ol is described in Ger. OS 36 33 033. The yields achievable with that catalyst (c. 60% of theoretical) are approximately the same as those observed with (Bu.sub.3 P).sub.2 NiBr.sub.2, but the catalytic activity with the latter system is greater than the catalytic activity according to Ger. OS 36 33 033. The mixture of nickel phosphite complexes which can be produced from nickel tetrakis(triphenyl phosphite) and an excess of sterically hindered triaryl phosphites according to said OS is preferably employed at 50.degree.-100.degree. C.
The above-described catalysts not only have major differences in catalytic activity, but frequently, even when their structures are similar, have widely differing selectivities in forming open chain and/or cyclic oligomers and in their degrees of oligomerization of the alkynes. As mentioned supra, most oligomerizations of 3-methyl-1-butyne-3-ol are carried out in the presence of nickel complexes (see, e.g., Jolly, P. W., in Wilkinson, G., and Stone, F. G. A., Eds., "Comprehensive Organometallic Chemistry", Vol. 8, 1982, pub. Pergamon Press, pp. 649 ff.); however, compounds of cobalt (J. Chem. Soc. C, 1967, 836), rhodium (J. Organomet. Chem., 240, 1982, 17), and palladium (Zh. Org. Khim., 19, 1983, 1853; J. Mol. Cat., 26, 1984, 363) have also been tested. With some of these catalysts the addition of reducing agents led to increased activity.
To date there has not been a persuasive explanation of why nickel shows particular catalytic activity in suitable ligand fields, and why under such circumstances the proportion of cyclic oligomers formed is often high. More recent publications (see J. Organomet. Chem., 258, 1983, 235; J. Mol. Catal., 48, 1988, 81) deal with the effect of electronic and steric factors of widely differing classes of phosphorus-containing ligands on the activity and selectivity of nickel-containing catalysts in the cyclooligomerization of 3-methyl-1-butyne-3-ol. E. Ger. Pats. 253,024 and 263,979 show ways of selective cyclotetramerization of propargyl alcohol and other 3-hydroxy-1-alkynes with the use of highly active catalysts, where nickel-containing precatalysts react with organylation agents or reducing agents, in specific molar ratios, and the cyclooligomerizations can be carried out at 50.degree.-110.degree. C. It is still unclear why only cyclotetramers are produced and why one cannot even detect traces of the homologous cyclic trimers with .sup.1 H-NMR spectroscopy. The results do indicate how difficult it has been heretofore to predict attainable selectivity and to influence the course of the reaction in a desired manner.
In addition to the often unsatisfactory selectivity toward formation of specific oligomers, the methods according to the state of the art in the production of cyclic trimers of 3-methyl-1-butyne-3-ol and other 3-hydroxy-1-alkynes have the following drawbacks:
relatively low catalyst activity, PA1 the need to use relatively large amounts of toxic and/or costly precatalyst stages, PA1 the need to satisfactorily dispose of corresponding amounts of the deactivated catalysts, and PA1 the difficulty in controlling the exothermic cyclooligomerizations in the presence of catalysts which frequently require a relatively long formation or incubation stage. PA1 a nickel compound soluble in the reaction medium, PA1 a phosphite of an ortho-substituted phenol, and PA1 an organometallic alkylating agent, PA1 R represents a branched or unbranched C.sub.1 -C.sub.20, particularly a C.sub.1 -C.sub.4, alkyl group, PA1 X represents hydrogen or chlorine, and PA1 n=0 or 1, PA1 an aprotic diluent or solvent, PA1 optionally an unconjugated diene, and PA1 optionally an amount of between 0 and 100 mol of the reactant 3-hydroxy-1-alkyne being cyclooligomerized per mol of the nickel compound, wherein said catalyst formation is carried out at 0.degree.-50.degree. C. (with effective intermediate temperatures of 10, 20, 30 and 40.degree. C.), and the cyclooligomerization of the reactant 3-hydroxy-1-alkynes added to the catalyst is carried out at a temperature of from 0.degree.-80.degree. C. (with effective intermediate temperatures of 10.degree., 20.degree., 30.degree., 40.degree., 50.degree., 60.degree.and 70.degree. C.), preferably between 30.degree.14 50.degree. C., and the diluent or solvent is added in amounts of &gt;200 parts by weight (pbw) per 100 pbw of the 3-hydroxy-1-alkyne, up to 1000 or 10,000 pbw of diluent or solvent per 100 pbw of alkyne with effective intermediate amounts being 300, 400, 500, 600, 700, 800, 900, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 8000, and 9000 pbw of solvent or diluent per 100 pbw of alkyne. PA1 a phosphite of an ortho-substituted phenol, PA1 an aprotic diluent, PA1 optionally an unconjugated diene, and PA1 optionally a portion of the 3-hydroxy-1-alkyne being cyclooligomerized, PA1 R represents C.sub.1 -C.sub.20 alkyl, PA1 X represents hydrogen or chlorine, and PA1 n=0 or 1,